A reduction in the pupil's response to affective sounds in psychopathy and related personality traits.

The pupil of the eye dilates in response to affective information, even if that information is not visual. We used this affective modulation of the pupil to examine the hypothesis that individuals with high traits of psychopathy have an insensitivity to emotional stimuli. We also examined general personality traits related to psychopathy. A sample of 120 healthy young men had their pupils monitored while they listened to sound clips that conveyed either neutral emotion (e.g., rain), negative emotion (e.g., a person screaming) or positive emotion (e.g., people laughing). Psychopathy and general personality traits were measured via self-report questionnaire. As expected, both the positive and negative emotional sounds produced greater dilation in the pupil size than neutral sounds. This affective modulation of the pupil was found to be reduced for the negative sounds for people high on the "callous/affective" components of psychopathy (the Affective facet of the SRP-4 and the Meanness scale of the TriPM) and the general personality traits of Reward Dependence and Cooperativeness. The results indicate that these callous traits of psychopathy and general personality may be underpinned by a reduction in the ability to effectively process or monitor emotional stimuli.